Due to multiple factors, expect to potentially pay more when booking in January. For low rates, November can be a great choice for travel to Bali. Flights to Bali from San Juan in November are about $1,215 on average during November, but can be found for as low as $890.
Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from San Juan to Bali as you normally would.